Journal of Molecular Evolution

, Volume 47, Issue 6, pp 640–648

Sponge Pax cDNA Related to Pax-2/5/8 and Ancient Gene Duplications in the Pax Family

  • Daisuke  Hoshiyama
  • Hiroshi  Suga
  • Naoyuki  Iwabe
  • Mitsumasa  Koyanagi
  • Naruo  Nikoh
  • Kei-ichi  Kuma
  • Fumihiko  Matsuda
  • Tasuku  Honjo
  • Takashi  Miyata

DOI: 10.1007/PL00006421

Cite this article as:
Hoshiyama, D., Suga, H., Iwabe, N. et al. J Mol Evol (1998) 47: 640. doi:10.1007/PL00006421

Abstract.

Members of the Pax gene family encode transcription factors containing a DNA-binding paired domain which is involved in developmental control and the formation of the central nervous system (CNS). The family members are classified into six classes or subfamilies, depending on the presence or absence of paired-type homeobox and octapeptide. To obtain rough estimates of times when the different classes of the Pax family diverged by gene duplication, we cloned and sequenced a Pax-related cDNA, sPax-2/5/8, from Ephydatia fluviatilis, a freshwater sponge, which encodes a paired-type homeobox and an octapeptide, in addition to a paired domain. A phylogenetic tree based on the paired domain sequences suggest that sPax-2/5/8 is a homologue of vertebrate Pax-2/5/8. It was also suggested that the majority of gene duplications that gave rise to distinct classes has been completed in the very early evolution of animals before the parazoan–eumetazoan split. Long after the ancient gene duplications, further gene duplications that gave rise to members in each subfamily occurred on the chordate lineages and completed before the fish–tetrapod split. This suggests that the major classes of the Pax genes involved in the formation of CNS characteristic of triploblasts had already existed long before the Cambrian explosion of triploblasts, and there is no direct link between the creation of new genes with novel functions and the Cambrian explosion. The pattern of gene diversification found in the Pax family is similar to those in five gene families involved in the signal transduction analyzed by us. Furthermore, the evolutionary rates of the Pax proteins have been shown to decrease with increasing organismal complexity during animal evolution.

Key words:Pax-2/5/8— Sponge — Gene duplication — Pax family — Cambrian explosion — Evolution

Copyright information

© Springer-Verlag New York Inc. 1998

Authors and Affiliations

  • Daisuke  Hoshiyama
    • 1
  • Hiroshi  Suga
    • 1
  • Naoyuki  Iwabe
    • 1
  • Mitsumasa  Koyanagi
    • 1
  • Naruo  Nikoh
    • 1
  • Kei-ichi  Kuma
    • 1
  • Fumihiko  Matsuda
    • 2
  • Tasuku  Honjo
    • 2
  • Takashi  Miyata
    • 1
  1. 1.Department of Biophysics, Kyoto University Graduate School of Science, Kyoto 606-8502, JapanJP
  2. 2.Department of Medical Chemistry, Kyoto University Graduate School of Medicine, Kyoto 606-8507, JapanJP